1. Field of the Invention
The present invention relates to a wire assembly apparatus, in particular for assembling wire harnesses and a method for assembling wires, in particular by using a wire assembly apparatus according to the invention.
2. Description of the Prior Art
A wiring harness is generally formed by arranging a multitude of long, processed wires on the wire arrangement board. Prior art long processed wires often include a spliced wire having a branch wire as shown in FIG. 17. The spliced wire is used to form a branch circuit for the wiring harness.
The above spliced wire is formed as follows. With reference to FIG. 17, an insulating sheath of a wire 1 as a main wire is peeled off in a specified position 1a, and an insulating sheath of a wire 2 as a branch wire is peeled off at an end 2a. Portions 1a, 2a of the wires 1, 2 where the sheath is peeled off are brought into contact with each other and connected by a connection terminal 3. This spliced wire needs to be formed before the wire arranging operation, and it is cumbersome to form it. Further, the spliced wires may get entangled during the wire arranging operation, thereby making this operation difficult. Therefore, there has been a demand for eliminating the spliced wires from the long processed wires for forming the wiring harness.
As a means to meet the above demand, a wiring harness producing method disclosed in Japanese Unexamined Patent Publication No. 58-192209 is known. According to this method, wires forming a wiring harness are divided into branch wires and straight wires to be connected with the branch wires, and terminal fittings are mounted at ends of the branch and straight wires. The branch wires and the straight wires are arranged on a wire arrangement board and connected with each other via connectors. In this way, there can be produced a wiring harness including the branch wires in conformity with the specification. However, this method requires a connector for each branch wire, leading to an increased production cost. In addition, the produced wiring harness has a large bulk of connectors. Accordingly, wiring is difficult if this wiring harness is used for an automotive vehicle to be installed in a narrow space such as the interior of a door.
As a means to solve the above problem, a wiring harness producing method disclosed in Japanese Unexamined Patent Publication No. 61-104505 is known. According to this method, branch wires and wires to be connected with the branch wires are pulled out of a bundle of main wires so as to gather portions to be connected in one place. The gathered portions to be connected are connected at one time by means of welding.
However, according to the latter wiring harness producing method, the branch wires and the wires to be connected with the branch wires are pulled out of the formed bundle of wires after all wires are arranged. Therefore, according to this method, the wire pulling operation to gather the portions to be connected needs to be performed separately from the wire arranging operation. In addition, the wire pulling operation is generally difficult and, therefore, takes a long time.
Thus, when a wiring harness is assembled on an assembly line according to this method, a maximum time, a so-called tact time, required for the wire pulling operation has to be longer than the times required for the other operations. This results in a poor production efficiency, thereby engendering a new problem: this method is not suitable for a line production.
Further, because of the difficulty to confirm the number of wires to be pulled out, some wires may not be pulled and a defective wiring harness may be manufactured.
The problem may be avoided if the wires to be pulled out later are separated from the other wires in advance during the wire arranging operation. However, this method requires devices for holding the separated wires during the wire arranging operation.
In view of the above, an object of the invention is to provide an improved wire assembly apparatus and an improved method for assembling wires, which allow a compact assembly of the wires at an advantageously improved production efficiency.